Also known as Sunset Yellow, Orange Yellow S, FD&C or C.I. 15985. This is a synthetic additive derived from coal tar, used as a colourant. Pets don’t need colour added into their food, not only is it potentially harmful, but also completely unnecessary. Yellow 6 can cause allergic reaction including gastric upset, vomiting, rash and swelling of the skin. In children, it has been shown to increase hyperactivity.